Candida albicans is the most frequently encountered fungal pathogen in humans, and is responsible for a variety of rnucocutaneous and systemic infections. There are a number of predisposing factors that contribute to Candida infections; however, the increasing number of immunocompromised patients (due primarily to imrnunosuppressive therapies and AIDS) has led to a sharp increase in the incidence of candidiasis. This fact, coupled with the limited arsenal of therapeutic agents, dictates that current research efforts focus on elucidating pathways that contribute to Candida virulence and on identifying novel targets for drug development. The long-term goal of this research program is to investigate whether a unique structural feature of fungal CCAAT-binding factors could serve as a target for antifungal compounds. The CCAAT-binding factor is a heterooligomeric transcriptional activator that is highly conserved evolutionarily in all eukaryotes; however, in fungi this transcription factor contains a novel subunit (termed Hap4p) that is not found in other eukaryotes. It is the unique interaction of this fungal-specific subunit with other components of the heteromeric complex that represents a potential target for drug development. The failure of Hap4p to interact with the DNA-binding components of the complex results in the loss of target gene expression. Thus, development of peptides or small molecules that inhibit this fungal-specific protein-protein interaction could offer a viable approach to combating fungal infections. The goal of the studies described in this proposal is to determine the regulatory function of the CCAAT-binding factor in C. albicans, and to examine whether it is important in the regulation of genes involved in virulence and pathogenesis, as the initial step toward exploring its potential as a therapeutic drug target. The proposed studies will address the following specific aims: 1) to generate mutants in the genes encoding the various subunits of the CCAAT-binding factor and evaluate their phenotypes; 2) to determine whether the CCAAT-binding factor is important for C. albicans virulence; and 3) to dissect the regulatory function of the CCAAT-binding factor.